HR: 0800h
AN: H21C-1352    [Abstracts]
TI: Analysis of Slug Tests in Bypassed Wells Using a Generalized Hvorslev-Style Model
AU: * Zenner, M A
EM: mzenner@zedat.fu-berlin.de
AF: Freie Universitaet Berlin, Inst. f. Geol. Wissenschaften, Malteserstrasse 74-100, Haus B, Berlin, 12249 Germany
AB: Non-linearities are still often underestimated in the analysis of aquifer tests today. In Berlin, many wells are furnished with a bypass observation tube flanged onto the main well riser. Hydraulic testing in such wells implies significant water level oscillations between the bypass tube and the primary well casing. The present work proposes an approximate method for the analysis of free non-linear water level oscillations induced by a slug test in a bypassed well. The procedure involves a transformation of the bypass and the casing head data into a bypass-corrected well casing head that could be expected inside the well riser if the bypass was not present. This bypass-corrected head response is analysed using a generalized non-linear Hvorslev-style model. We illustrate the method by an example analysis of a set of six overdamped slug tests and comment upon how non-linear hydraulic head losses might deterministically be acknowledged. The investigated set of slug tests was designed to cover classical linear as well as non-linearly distorted head responses by employing differing radii packer flow-through tubes in conjunction with different initial head displacements. It is shown that the dependency of measured head responses on changes of the cross sectional area along the flow path inside the wellbore could consistently be modeled by incorporating minor head losses based on the Borda-Carnot formula and turbulent losses based on the formula of Colebrook. Furthermore, the analysis of the experimental data reveals that responses obtained from the non-linear model reduce to classical linear responses when using a sufficiently wide packer flow-through pipe. The insight gained about the characteristics of wellbore-internal non-linear hydraulic losses might help to differentiate head response anomalies related to wellbore hydraulics and non-linear aquifer flow phenomena, respectively.
DE: 1828 Groundwater hydraulics
DE: 1829 Groundwater hydrology
DE: 1847 Modeling
DE: 1849 Numerical approximations and analysis
SC: Hydrology [H]
MN: Fall Meeting 2005